Merge remote-tracking branch 'origin/5.5' into 10.1

1 files changed, 25 insertions, 2 deletions

diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 29fc3f80ed0..5b96c15bff5 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -16158,8 +16158,31 @@ static Field *create_tmp_field_from_item(THD *thd, Item *item, TABLE *table,
 {
   Field *UNINIT_VAR(new_field);
   DBUG_ASSERT(thd == table->in_use);
-  new_field= item->Item::create_tmp_field(false, table);
-    
+  if (item->type() == Item::FUNC_ITEM &&
+      static_cast<Item_func*>(item)->functype() == Item_func::SUSERVAR_FUNC)
+  {
+    /*
+      A temporary solution for versions 5.5 .. 10.3.
+      This change should be null-merged to 10.4.
+
+      Item_func_set_user_var is special. It overrides make_field().
+      by adding a special branch `if (result_field)...`.
+      So it's important to preserve the exact data type here,
+      to avoid type mismatch in Protocol_text::store_longlong()
+      See MDEV-15955.
+
+      Other Item_func descendants are not affected by MDEV-15955.
+      They don't override make_field() so they don't use result_field
+      when initializing Send_field.
+
+      This is properly fixed in 10.4 in the method
+      Item_func_user_var::create_tmp_field_ex().
+    */
+    new_field= item->tmp_table_field_from_field_type(table, false, true);
+  }
+  else
+    new_field= item->Item::create_tmp_field(false, table);
+
   if (copy_func &&
       (item->is_result_field() || 
        (item->real_item()->is_result_field())))